class MyFace {
  int npoints = 0; //the number of points
  MyPoint [] points; //array of points

    MyFace (){
    points = new MyPoint[0];
  }
  MyFace(MyPoint[] inPoints){
    points = new MyPoint[inPoints.length];
    npoints = inPoints.length;
    for(int i=0; i<inPoints.length; i++)
      points[i] = new
        MyPoint(inPoints[i].x, inPoints[i].y, inPoints[i].z);
  }
  void addPoint(float addX, float addY, float addZ){
    npoints++;
    points=(MyPoint[])append(points, new MyPoint(addX,addY,addZ));
  }
  void move(float xoff, float yoff, float zoff){
    for(int i=0; i<npoints; i++)
      points[i].move(xoff, yoff, zoff);
  }
  void rotatex (float angle, MyPoint ref) {
    for(int i=0; i<npoints; i++)
      points[i].rotatex(angle, ref);
  }
  void rotatey (float angle, MyPoint ref) {
    for(int i=0; i<npoints; i++)
      points[i].rotatey(angle, ref);
  }
  void rotatez (float angle, MyPoint ref) {
    for(int i=0; i<npoints; i++)
      points[i].rotatez(angle, ref);
  }
  void scale(float xs, float ys, float zs, MyPoint ref){
    for(int i=0; i<npoints; i++)
      points[i].scale(xs, ys, zs, ref);
  }
  void draw(){
    beginShape(QUADS);
    for(int i = 0; i < npoints; i++){
      vertex(points[i].x,points[i].y, points[i].z);
    }
    endShape(CLOSE);
  }

  boolean isVisible() {
    float x1, y1, x2, y2, norm=0;
    int ahead1, ahead2;
    for (int i=0; i<npoints; i++) {
      ahead1 = i+1;
      ahead2 = i+2;
      if(i == (npoints-2)) ahead2 = 0;
      if(i == (npoints-1)) {
        ahead2=1;
        ahead1=0;
      }
      //make vector 1
      x1 = points[ahead1].xscreen() - points[i].xscreen();
      y1 = points[ahead1].yscreen() - points[i].yscreen();
      //make vector 2
      x2 = points[ahead1].xscreen() - points[ahead2].xscreen();
      y2 = points[ahead1].yscreen() - points[ahead2].yscreen();
      //cross product
      norm += (x1*y2 - y1*x2);
    }
    if(norm > 0.0) return false; //if clockwise
    else return true; //else ccw
  }


}